This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Effective strategies for HIV prevention are urgently needed, but recent failures in key vaccine and 'microbicide'clinical trials highlight the need for new approaches validated in relevant animal models. However we now know that CCR5 is the major receptor for viral fusion and that RANTES and RANTES analogs can bind CCR5, making it inaccessible for viruses. Thus we have been developing RANTES analogs as microbicide candidates. However a recent report by Achour et al. suggested that primary T cells harbor pools of intracellular CCR5 which could render such an approach useless if receptors were rapidly re-expressed after blockage. By using a series of complementary techniques to measure CCR5 expression (antibody labeling, Western blot, qRT-PCR), we established that intracellular pools of CCR5 do not exist and that the results obtained by Achour et al. were false-positives that arose due to the generation of irrelevant binding sites for anti-CCR5 antibodies during fixation and permeabilization of cells.